In the medical service system, when the number of expert seats is in short supply, it is difficult to make full use of hospital resources by the traditional queuing method. Without changing the existing resources, an overflow model with triage in a Markov queuing system is established by overflowing a part of patients in the expert queue into the general queue under a certain condition to allocate reasonably the capacity of each outpatient. The numerical simulation using ProModel, a simulation software, shows that the average queue length, waiting time and other service indices are better than the traditional models.